How o i get the awnser to 9s+3=57 i need asap im in 8th grade

First subtract 3 from both sides of the equal sign. 
9s + 3 = 57
      - 3     -3
9s = 54

Then divide both sides by 9.
9s = 54
/9     /9
s = 6

You can check it by plugging it back into the equation.
9s + 3 = 57
9 * 6  + 3= 57
54 + 3 = 37
57 = 57
Yep! It's correct! :)

Hope that helped. Algebra can be tricky sometimes I know but it's really just balancing equations.